Defect detector and stop motion control system



DEFECT DETECTOR AND STOP MOTION CONTROL SYSTEM Filed Jan. l5, 1964 R J m, T R A M H. I

4 Sheets-Sheet 2 T0 POWER SUPPLY FOR LIGHT BULBS INVENTGR JAMES HENRY MARTIN, JR.

BY j/Wg@ am 2 o 2 E B U 1| E m F 0 Tl S M B D FIG.

TYPICAL c8 REcHARcE cuRvE o 2 3 4 5 lo TIME (sEc.)

ATTORNEY May 2, 1967 J. H. MARTIN, JR 3,317,734

DEFECT DETECTOR AND STOP MOTION CONTROL SYSTEM 4 Sheets-Sheet 3 Filed Jan. l5, 1964 ATTORNEY DEFECT DETECTOR AND STOP MOTION CONTROL SYSTEM Filed Jan. 15, 1964 May 2, 1967 J. H. MARTIN, JR

4 Sheets-Sheet 4 INVENTOR JAMES HENRY MARTIN, JR.

z SN ATTORNEY United States Patent O 3,317,734 DEFECT DETECTGR AND STOP MOTION CONTRGL SYSTEM .lames Henry Martin, fir., Waynesboro, Va., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Filed Jan. 15, 1964, Ser. No. 337,831 4 Claims. (Cl. Z50- 214) This invention relates to the processing of textile rope or tow, and particularly concerns monitoring the appearance and lateral motion of rope or tow moving at high lineal speeds and thereby detecting or predicting malfunction of the process so that it can be stopped without material damage to the apparatus used in the process. By textile rope or tow is meant an assemblage of a large number of substantially parallel multifilarnent continuous yarns in a generally ribbon or rope shaped form having a total weight per unit length of up to several hundred thousand denier.

There exist in the art many devices for detecting a break or fiow in continuously running material. Some are mechanical, some employ ultrasonics, and some use photoelectric `detecting components. processing a heavy rope at high speeds, these devices sometimes fail to operate rapidly enough to prevent heavy accumulation of material in certain confined spaces in a processing machine or fail to detect a wrap of a part of the rope around a roll which may build up to dangerous levels before any malfunction is detected. On the other hand a splice in part of the rope or a transient splitting or momentary loss of a section may cause the usual detector to stop the machine unnecessarily. Finally, it has been found that an unsupported length of rope travelling rapidly between two rolls will often `develop lateral vibration or flutter before malfunction occurs and therefore measurement of fiutter can enable prediction of malfunction.

The primary object of this invention is to provide apparatus for detecting partial and full breaks in a rapidly moving rope of textile fibers, and to predict a break or other malfunction based on the detection and measurement of the severity of non-uniform movement or fiutt'er in the rope. A further object is to provide apparatus for signalling a break or impending malfunction and stop the rope drive to prevent damage to the processing equipment.

These objectives are attained by this invention which comprises, in a machine for transporting textile rope between two sets or rolls at least one of which is driven, a photoelectric scanner that in one embodiment includes at least three light sources on one side of the rope and an equal number of resistance type photosensitive devices on the other side of the rope, each aligned respectively with a corresponding light source. In addition there is provided means to stop the system in response to light being detected bv all the photosensitive detectors. Further, means are included to note lateral movement of the rope as well as the frequency thereof, and means to stop the system if the frequency is substantial. For these purposes there can be employed one branch circuit responsive to the photosensitive detectors comprising a -preamplifier, a time delay subcircuit, an amplifier-pilot relay with hold and reset, control relay and motor contactors, alarm circuits and light indicator relay; a second circuit, receiving signals from the preamplifier, comprising a pulse driver, an electromechanical counter, and a pulse inverter-alarm relay; and a third circuit, receiving signals from the driver through an RC integrator and bias selector subcircuit for a break predictor-excessive Hutter-relay with reset, and control relay for drive motor stop contactor and indicator light.

However, when A preferred embodiment of this invention is described in the following specification wherein reference is made to the accompanying drawings in which:

FIGURE l is a block diagram of elements that can be used in the invention;

FIGURE 2 is an isometric schematic drawing of a scanning member for use in the invention;

FIGURE 3 is a schematic partial circuit diagram showing a preamplifier, time delay, amplifier-relay with reset, break detector-alarm and drive motor stop control;

FIGURE 4 is a schematic circuit diagram of a flutter counter, fiutter alarm delay selector, excessive flutterbreak predictor with reset and drive motor stop control; and

FIGURE 5 is a diagram showing a typical grid bias variation with time during rope flutter.

In FIGURE l there is shown the basic functional elements of this invention comprising a scanner 10 with three photoelect-ric detectors and an optional mechanical plunger backup switch 12, details of which will be given hereinafter. A cable 14 connects the scanner to a preamplifier 16, the output of which is Carried over line 18 to a time delay subcircuit 20 which feeds an amplifierpilot relay 22 having an external hold and reset circuit 24 operating through cable 26 and an indicator light 23 operating through line 21. The output of amplifier-relay 22 is carried through line 25 to control relay 27 and then over lines 28, 30 and 32 to, respectively, a drive motor stop circuit 34, an alarm control relay energized lamp circuit 36 and an optional logic relay circuit 38. The output of preamplifier 16 is also carried over line 40 to counter driver and pulse Shaper circuit 42. The output of this latter circuit 42. is directed first over line 44 to an electromechanical counter 46 and over lines 4S and S0 first, to a pulse inverter/fiutter alarm-relay circuit 52 and then over cable 54 to a fiutter alarm light and horn circuit 56. Another signal from circuit 42 is carried over line 50 to RC integrator and bias selector 58 and over cable 60 to the break predictor and excessive flutter pilotrelay circuit 62, having reset circuit 64 connected through cable 66 and indicator light 69 connected by line 67. The output of circuit 62 is also carried lover line 63 to control relay 65, to a drive motor stop control circuit 72 by line 68, to remote indicator light 71 by line '70, and optionally over line '76 to the logic relay circuit 38.

In FIGURE 2 scanner assembly 10 is shown to comprise a rectangular block with a slot 101 shaped for passage of rope passing in a straight line between two sets of rolls. The two sets of rolls indicated may, for example, be constant torque pull rolls and crimper rolls in an apparatus line adapted to make and then crimp rope. Such apparatus is conventional and is well known, and generally includes a plurality of rope-ribbon supply lines which are fed through a series of driven and idler rolls. The rope-ribbons are then directed to stacking guides to form a single tow or rope 100. After steaming, the rope passes through constant torque pull rolls, shown generally as 103 in FIGURE 2, and then to crimper rolls 107. After crimping, the rope or tow can be stored, used as such, cut to staple, or otherwise employed in a manner that is of no materiality to the present invention. Normally at least one of the sets of rolls 103 and 107 is driven. The scanner assembly 10 in this embodiment is located about the moving rope 100 between these sets of rolls. It will be appreciated that one or more driving means is associated with the rope forming apparatus and supplied with power of suitable characteristics for each driven part in the system. In the discussion in this application reference is made to but a single drive motor. It should be understood that a single driving means or a plurality m-ay actually be used; however, in the latter event all must be controllable at a single point for stopping purposes. Consequently, it will be understood that reference to the drive motor is to be construed broadly to indicate that stopping the entire system is involved, without regard to the actual number of motors that may be employed.

The scanner is shown broken away to reveal a light source 104, lens 106 and photosensitive device 108 in line. Similar light source and detector assemblies (not shown) are aligned with lenses 106' and 106". Lenses and detectors may be recessed if protection is needed. The three sources of light are connected in parallel with leads passing through conduit 102 to a low voltage power supply not shown. Similarly the three photosensitive devices 108, 108 and 10S (FIGURE 3) are connected in parallel and with leads extending through conduit 110 (forming cable 14 of FIGURE l). The light beam from the middle assembly of light source, lens and photo device is aligned substantially With the center of the moving rope 100 and the other two light beams are focused near the two side edges of the rope at distances from the edges that will avoid false stops from minor edge instability but close enough to sense lateral movement characterized as flutter. The photo devices are of the photo resistive type such as Texas Instruments Inc., Type IN2175. r:The light sources are straight filament lamps such as Westinghouse No. 44. The lenses are double convex type such as Edmund Scientific Co., mm. diameter with a 13.1 mm. focal length. Of course other commercially lavailable devices can be used as well, if desired. Mounting recepticals are provided for the light bulbs and photo devices and adjusting screws may be provided to align each assembly as needed. When it is necessary to provide for ropes of larger width, the scanner may be constructed in two or more separable parts such as by division along a plane indicated by dotted line 113. In some cases, the assembly is provided with vapor proof seals and possibly with air purge arrangements in order to prevent vapors or liquids from penetrating the assembly. A mechanical plunger switch 12 may be provided as a backup switch in parallel with the photoelectric devices such that it will be activated in case rope builds up in the area of the scanner, thus blocking oft" the lights and preventing a machine stop being activated in the usual manner by the light sources,

FIGURE 3 is a schematic diagram of the essential elements of the rope break detector. Here the three photo sensitive devices 108, 108 and 108 are shown connected in parallel and their two leads 120, 121 comprising cable 14 of FIGURE l. Optional backup pressure switch 12 is also connected across the -two leads 120 and 121. Lead 120 is shown connected to the base of a rst transistor 122.- This transistor is employed as a preamplifier and has its emitter connected to ground and its collector connected through resistor R1 t-o a D.C. power supply over line 124. Power to line 124 is provided from a conventional D.C. power supply (not shown) furnishing in this case approximately 30 volts D.C. The second lead 121 from the photosensitive devices is connected to current limiting resistor R2 and thense also to the D.C. power'line 124. An RC time delay circuit comprising adjustable capacitor C1 and resistor R2, with diode 126 connected around C1, transmits a signal from transistor 122 to the base of a second transistor 128 in the amplifier relay 22. The collector of this latter transistor is con-4 nected through resistor R1 to ground. A conventional bias temperature compensating circuit 130 is connected through line 132 to a point between the collector of transistor 128 and resistor R4. The base of transistor 128 is also connected through adjustable resistor R5 and resistor R6 to line 124 of the D.C. power supply. The emitter of transistor 128 is connected through resistor R2 to the D.C. power supply line 124- as well as through resistor R7 and resistor R8 to ground. A wire 134 is connected from the collector of transistor 128 to the base of a third transistor 136. The emitter of this latter transistor 136 is connected through resistor R8 to ground and the collector is connected to the operating coil 138 of a pil-ot relay 140 and through coil 138 to a junction between resistors R5 and R6. This collector is also connected through diode to D.C. power line 124. Relay 140 contains two sets of contacts 142 and 144, which are normally open. One side of contacts 142 is connected to the collector terminal of transistor 136 and the other side of contacts 142 is connected to resistor R10 and then through a normally closed push type switch 146 of the hold and reset system 24 to ground. The second set of contacts 144 in relay 140 are connected on one side to an A.C. power source and on the other side through line 149 to the operating coil 148 of control relay 27 and thence to ground by line 150. Line 21 connects line 149 to a control actuated indicator lamp 23 and on to ground. Relay 27 contains two sets of contacts 152 and 154, also both normally open. Contacts 152 are connected on one side to ground and the other side to a remote control relay energized indicating light and alarm circuit 36, and thence to an A.C. power source. The other set of contacts 154 are connected to the drive motor stop supervisory `circuit 34. Circuit 36 may be a panel light and/0r a horn or other alarm indicating device, either visual or aural. Finally .a wire 40 is connected from the collector of transistor 122 to the flutter circuit 42 detailed in FIGURE 4 and described below.

In FIGURE 4 the collector output of preamplifier transistor 122 of FIGUR-E 1 is shown connected over line 40 to a capacitor C2 and thence branching to resistors R11 and R12. The other terminal of current limiting resistor R11 is connected to the control grid of a gas iilled thyratron tube 160, and the second terminal of the resistor R12 is connected to ground. The plate of thyratron is connected through line 44 to coil 162 of an electromechanical counter 46 and thence through bleed resistor R15 to a B+ plate power supply (not shown). An armature 164 of the counter is connected mechanically to a count indicator 166; a iilter capacitor C11 is connected across coil 162. A pulse capacitor C4 is connected between bleed resistor R15 andthe supressor grid of tube 160. A bias current resistor R16 is connected between the plate supply and the screen grid of tube 160.

This screen grid is further connected through feedback resistor R14 to the cathode of tube 160 and through cathode bias resistor R12 to ground. A ltering capacitor C3 is connected between the cathode of tube 160 and ground. The line 48 of FIGURE 1 is shown now in more detail in FIGURE 4 to be connected from the common point between counter coil 162 and plate bleed resistor R15, and is further connected in series through a resistor R17, a capacitor C10, a diode 168 and a further current limiting resistor R111 to the control grid of second thyratron tube 170. From a point between capacitor C10 and diode 168, there is connected a diode 172, the other terminal of which is connected to line 174 coming from a negative D.C. grid power supply, not shown. From the other side of diode 168, a resistor R19 is also connected to line 174. The plate terminal of tube is connected through an alarm relay coil 176to line 180 leading to a high voltage A.C. plate supply source, not shown. A smoothing and voltage limiting capacitor C5 and resistor R20 in series are connected in parallel with relay coil 176. Relay 178 contains two sets of contacts 182 and 184, both of which are normally open. One side of both sets of contacts is connected to ground. One side of contacts 182 is connected through a horn 186 to an A.C. power source (not shown). Similarly, one side of contacts 184 is connected through an indicator light 188 and thence to the A.C. source. Finally, the suppressor grid of tube 170 is connected to the cathode and thence to ground through a current limiting resistor R22.

Returning to tube 160 (FIGURE 4), a line 50 is connected from the cathode' of tube 160 through capacitor C7, diode 192 and over line 194 to a current limiting resistor R22 to the control grid of a third thyratron tube 202. From a point between capacitor C7 and diode 192, a second diode 190 is connected with its opposite terminal connected through by-pass capacitor C6 to ground. A grid leak resistor R21 is connected around diodes 190 and 192. From the common terminal of capacitor C6 and resistor R21 a line 196 is connected first to the slider terminal 199 of potentiometer 198 and second to one side of variable capacitor C8. The other terminal of capacitor C8 is connected through the current limiting resistor R22 to the control grid of tube 202. Power is supplied to potentiometer 198 from a negative grid bias supply (not shown) over line 200 and thence through the potentiometer to ground. Line 200 may be connected to line 174 and a common supply used. The plate of tube 202 is connected through coil 204 of pilot relay 206 and thence through a normally closed switch 208 to line 180 of the high voltage A.C. plate supply. A filter capacitor C12 is connected across coil .204. Relay 206 contains two sets of normally open contacts 210 and 212. One side of contacts 210 is connected to the plate terminal of tube 202 and the other side of this set of contacts is connected through a hold circuit containing a diode 214 in parallel with a capacitor C9 and thence to ground. The other set of contacts 212 is connected on one side over line 63 through operating coil 216 of control relay 65 and thence by line 217 to ground. Line 63 is also connected by line 67 to control actuated indicator lamp 69 and thence to ground. On the other side of contacts 212 there is connected a conventional A.C. power source. Relay 65 contains two sets of normally open contacts 220 and 222. One side of contacts 220 is connected to ground and the other to line 70 of remote control relay energized indicating lamp 71. The other set of contacts 222 is connected over cable 68 to drive motor stop control circuit 72.

In operation this device performs three basic functions: (l) rope break detection, alarm, and automatic drive stop, (2) rope defect counting and signaling, and (3) rope utter integration and break prediction with subsequent automatic drive stop and signaling. When acceptable rope is passing smoothly through slot 101 in scanner 10, each of the three light source beams are interrupted or covered so that no appreciable light falls on the detectors and they are each in their high resistance state. If, however, the rope breaks upstream of the rolls feeding rope toward the scanner 10, the light sources will be uncovered and light will impings on the detectors changing them to the low resistance state. This will cause a substantial electrical pulse of considerable duration to pass over line 14 to the preamplifier and thence over lines 18 and 40 to the various subcircuits. Similarly, loss of part of the rope causing a thin spot in the center or near the edges, due to some malfunction upstream (such as a wrap of part of the rope around a roll) will cause one or more of the sensors to receive sufficient light to switch to a lower resistance state, but this will result in a lesser current flow than when all sensors are receiving light, as in the instance of a rope break. Since the sensors are in parallel, this will furnish a signal to the preamplifier as before. A transient loss of part of the rope crosssection or lateral vibrations (flutter) in the progress of the rope through the scanner will cause pulses of current having varied durations and frequencies of occurrence.

The adjustable time delay circuit 20 (FIGURE l) comprising variable capacitor C1, diode 126, and resistor R3 (FIGURE 3) makes it possible to preselect the magnitude of pulse duration which will energize amplifierrelay 22 (FIGURE l) and as a result operative drive motor stop control and the alarms of circuits 34 and 36, respectively. In the amplifier-relay circuit 22 as detailed in FIGURE 3, the transistors 128 and 136 operate, with hold and reset circuit 24, to maintain pilot relay 140 in the energized condition following a pulse caused by a rope break. lOnce energized, the circuit, comprising the DC. power supply in line 124 through resistor R6, coil 138, and contacts 142 of relay 140, resistor R111, switch 146 to ground, holds transistor 136 in its operating state until switch 146 is opened thus resetting the amplifierrelay circuit 22. Thus an upstream break or malfunction of predetermined length of time duration will cause the process to be stopped and signals energized. Should a break occur below the scanner and the rope accumulate above the scanner, the sensors might in some cases not be uncovered and the automatic stop not energized. To take care of this possibility pressure switch 12 of FIG- URES 1, 2 and 3 is placed on the top surface of the scanner adjacent to t-he slot 101 and wired in parallel with the detectors so that the -break detector circuit will then be energized if rope piles up and presses switch 12.

Should the defect scanned provide a signal of a dura` tion shorter than the aforementioned preselected value, the signal would not operate the circuit 22 of FIGURE l and FIGURE 3 because of the operational parameters thereof, but would be conducted over line 40 to the other circuits including circuit 42, 52, 58 and 62. Each high speed transient of this type is accepted by the thyratron (FIGURE 4) and associated circuit so that, when thyratron 160 fires, an electromechanical counter 46 is actuated and a pulse is further transmitted over line 48 to circuit 52 comprising thyratron tube 170 and associated circuitry such that thyratron 170, when it is fired, operates (through relay 178) an audible signal such as a horn and an indicator light. Grid leak resistor R19 is selected to provide a time delay in the resetting of thyratron such that the alarm and indicating devices are energized for a brief period such as, for example, one second for each occurrence of a high speed transient such as a flutter.

These high speed transients may be repetitive if, for example, the rope starts to vibrate or flutter in its progress through the scanner 10. Flutter may be caused by a defective rope, incorrectly positioned guides, incorrectly spaced rolls, malfunction downstream such as uneven roll takeup of the rope due, for example, to excessive pressure in a crimper or other crimper malfunction when the rope is fed to a stutter box type crimper. A rope break or other malfunction may be predicted on the basis of the number of flutter counts in a given length of time. This is done by means of the RC integrator and bias selector circuit 58 and the associated break predictor-excessive flutter stop circuit 62. When a flutter occurs, which res thyratron 160, a signal is also introduced into circuit 58 through coupling capacitor C7. Prior to receiving a pulse through capacitor C7 the grid thyratron 202 is negatively biased to a voltage level determined by the setting of slider 199 of the potentiometer. When a signal is received through C7 its polarity is such that the negative grid bias on tube 202 is reduced by a small adjustable increment. In between signals the grid bias is returned toward its original level at a rate adjusted by the value of capacitor C8 and bleed bias resistor R21. Thus by adjustment of the circuit constants in the circuit 58 a preselected number of flutter pulses is required within a preselected length of time before the grid vbias is reduced to an extent sufficient to fire thyratron 202. FIGURE 5 shows a typical graph of grid bias change with time as a result of flutter. When tiring does occur relays 206 and 65 are energized which in turn operate the drive motor automatic stop 72 and the remote control relay energized indicator light 71, respectively. In circuit 58 the resistor R21 forms an RC time constant circuit with the integrating capacitor C8. In one embodiment, this time constant is adjusted to be approximately 30 seconds. Therefore, flutter incidents occurring less frequent than 30 seconds apart will be completely ignored by this circuit. Once the thyratron 202 fires, the circuit provided by contacts 210 of relay 206 which connects the plate of tube 202 through diode 214 and capacitor C9 (in parallel) to ground, prevents relay 206 from being de-energized and therefore it remains energized until an operator manually opens switch 208, thus dropping the voltage on the plate of this tube 202 and relay coil 204 resetting this thyratron hold circuit. With this thyratron firing thereby indicating a flutter condition that is of severity that probably will cause a break, it is necessary that the system be shut down. This occurs upon current passing through coil 204, closing contacts 212 and thereby activating coil 216. The latter coil closes contacts 222 shutting off the drive motor 72.

Thus there is provided by this invention an automatic signalling and drive motor stop system based on the use of photoelectric detectors which, when applied to a textile rope being transported in a straight line free span between two sets of rolls, at least one set being driven, not only detects breaks in the rope and operates automatic drive stop and break signalling apparatus, but also detects splits in the rope, transient defects and flutter; counts and signals these defects and furthermore predicts an impending serious malfunction on the basis of flutter frequency and operates an automatic drive motor stop device when utter frequency exceeds a preselected level.

In some applications it may be necessary to employ more than one of the devices of this invention in connection with an integrated rope processing machine. In addition other break or defect detecting devices may be employed such as, for example, knot switches, which operate when a knot of suflicient size is brought to the rope processing machine, or in-dividual ribbon break detectors when the rope is made up of individual smaller ribbons of fibers which pass through part of the process individually before combining into the rope. When this is the case, these various devices are electrically interlocked to cause automatic stopping and at the same time may opcrate a single alarm from these several devices. In addition, relay logic may be provided which suppresses second or later outputs from the various devices and therefore the identity of the device which first detected the machine malfunction and operated the automatic drive stop device is indicated.

This invention has been illustrated above by descrip-l tion of a preferred embodiment. Additional embodiments or modifications such as for example use of other trigger devices than thyratrons will be apparent to one skilled in the art without -departure from the inventive concept which, accordingly, -is intended to be limited only by the scope ofthe following claims.

What is claimed is:

1. In combination with rope forming apparatus including driving means and spaced sets of rolls between which rope passes and in which at least one of the sets of rolls is driven, scanning means about the rope between the sets of rolls, the scanning means comprising a light source aligned on the path of the rope between the sets of rolls and focused transverse to the normal direction of rope movement with a predetermined field ldefining slightly less than a normal width of rope, and a photoelectric detector aligned With the light source to receive light in the partial and total absence of rope therebetween, first means comprising a pre-amplifier providing an output signal to an amplifier-relay operative to stop said driving means on an extended signal from the photoelectric detector, means responsive to another output signal from the pre-amplifier comprising a first trigger device adapted to function on any signal from the pre-amplifier, signalling means responsive to an output signal from the trigger device, second means responsive to another output signal of predetermined polarity from the trigger device comprising a second trigger device subject to a predetermined bias of polarity opposite to said predetermined polarity, said second trigger device being adapted to function upon changing of its bias to a predetermined level by successive output signals from the first trigger device, and relay means to stop the driving means operative upon the functioning of the second trigger device.

2. A combination in accordance with claim 1 including means to apply bias to said second trigger device to return its bias to the predetermined level in a predetermined period of time, whereby the second trigger device is prevented from functioning upon receipt of a plurality of signals that are substantially spaced.

3. In combination with rope forming apparatus including driving means and spaced sets of rolls between which rope passes and in which at least one of the sets of rolls is driven, scanning means about the rope between the sets of rolls, the scanning means comprising a plurality of light sources aligned on the path of the rope between the sets of rolls and focused transverse to the normal direction of rope movement with a predetermined field defining slightly less than a normal width of rope, and a plurality of photoelectric detectors aligned with the light sources to receive light in the partial and total absence of rope therebetween, first means comprising a pre-amplifier providing an output signal to an amplier-relay operative to stop the driving means on an extended signal from all the photoelectric detectors, means responsive to another output signal from the pre-amplifier comprising a first thyratron adapted to fire on any signal from the preamplifier, signalling and counting means responsive to an output signal from the thyratron, second means responsive to another output signal of predetermined polarity from the thyratron comprising a second thyratron subject to a predetermined grid bias of polarity opposite to said predetermined polarity, said second thyratron being adapted to fire upon lowering of its grid bias to a predetermined level by successive output signals from the first thyratron, relay means to stop the driving means operative upon the firing of the second thyratron, and signalling means to indicate the stopping of the driving means.

4. A combination in accordance with claim 3 including means to apply grid bias to said second thyratron to return the bias thereon to the predetermined level in a predetermined period of time, whereby the second thyratron is prevented from firing upon receipt of a plurality of signals from said first thyratrons that are substantially spaced.

References Cited by the Examiner UNITED STATES PATENTS 2,229,638 1/1941 Chamberlin et al. Z50- 219 2,809,297 lO/1957 Hartwig et al 324--78 X 2,999,208 9/1961 Ruehlemann 328-186 X 3,043,991 7/1962 Schneider et al. 250-219 3,105,151 9/1963 Nash 250-219 3,257,559 6/1966 McMullen 250-219 References Cited by the Applicant UNITED STATES PATENTS 2,962,596 ll/l960 Leimer et al. 3,055,200 9/ 1962 Meimers et al.

FOREIGN PATENTS 612,024 1/ 1961 Canada. 838,176 6/1960 Great Britain. 905,318 9/ 1962 Great Britain.

RALPH G. NILSON, Primary Examiner.

M. A. LEAVITT, Assistant Examiner. 

3. IN COMBINATION WITH ROPE FORMING APPARATUS INCLUDING DRIVING MEANS AND SPACED SETS OF ROLLS BETWEEN WHICH ROPE PASSES AND IN WHICH AT LEAST ONE OF THE SETS OF ROLLS IS DRIVEN, SCANNING MEANS ABOUT THE ROPE BETWEEN THE SETS OF ROLLS, THE SCANNING MEANS COMPRISING A PLURALITY OF LIGHT SOURCES ALIGNED ON THE PATH OF THE ROPE BETWEEN THE SETS OF ROLLS AND FOCUSED TRANSVERSE TO THE NORMAL DIRECTION OF ROPE MOVEMENT WITH A PREDETERMINED FIELD DEFINING SLIGHTLY LESS THAN A NORMAL WIDTH OF ROPE, AND A PLURALITY OF PHOTOELECTRIC DETECTORS ALIGNED WITH THE LIGHT SOURCES TO RECEIVE LIGHT IN THE PARTIAL AND TOTAL ABSENCE OF ROPE THEREBETWEEN, FIRST MEANS COMPRISING A PRE-AMPLIFIER PROVIDING AN OUTPUT SIGNAL TO AN AMPLIFIER-RELAY OPERATIVE TO STOP THE DRIVING MEANS ON AN EXTENDED SIGNAL FROM ALL THE PHOTOELECTRIC DETECTORS, MEANS RESPONSIVE TO ANOTHER OUTPUT SIGNAL FROM THE PRE-AMPLIFIER COMPRISING A FIRST THYRATRON ADAPTED TO FIRE ON ANY SIGNAL FROM THE PREAMPLIFIER, SIGNALLING AND COUNTING MEANS RESPONSIVE TO AN OUTPUT SIGNAL FROM THE THYRATRON, SECOND MEANS RESPONSIVE TO ANOTHER OUTPUT SIGNAL OF PREDETERMINED POLARITY FROM THE THYRATRON COMPRISING A SECOND THYRATRON SUBJECT TO A PREDETERMINED GRID BIAS OF POLARITY OPPOSITE TO SAID PREDETERMINED POLARITY, SAID SECOND THYRATRON BEING ADAPTED TO FIRE UPON LOWERING OF ITS GRID BIAS TO A PREDETERMINED LEVEL BY SUCCESSIVE OUTPUT SIGNALS FROM THE FIRST THYRATRON, RELAY MEANS TO STOP THE DRIVING MEANS OPERATIVE UPON THE FIRING OF THE SECONE THYRATRON, AND SIGNALLING MEANS TO INDICATE THE STOPPING OF THE DRIVING MEANS. 